CLASSIFICATION OF PORPITA
PHYLUM :- COELENTRATA (Tissue grade, diploblastic and acoelomate. )
CLASS :- HYDROZOA (The hydroids and craspedote medusa )
ORDER :- SIPHONOPHORA (Polymorphic colonies with various polypoid and medusoid zooids.)
SUB-ORDER :- PHYSOPHORIDA (Upper end of colony contains float or pneumatophore, without swimming bells or bracts and with simplified cormidia. )
FAMILY :- CHONDROPHORAE (Float forms a disk like structure.)
GENUS :- Porpita
It is found along the South Atlantic coast and occasionally near U.K. coast.
HABIT AND HABITAT
Porpita is marine and colonial, found in warm seas.
GENERAL CHARACTERSTICS OF PORPITA
- It superficially resembles a medusa. It is most modified siphonophore. The stem is shortened to a flat coenosarc which along with float forms a rounded disk having several concentric air chambers.
- Body is discoidal, enclosing a chambered, chitinous and porous shell, having air corresponding with pneumatophore of Physalia.
- A large gastrozooid, having central mouth is encircled by several blastostyles.
- Margin of disk contains numerous dactylozooids or tentacles armed with nematocysts.
- Nectocalyces or swimming bells are absent.
- Each air chamber opens to outside by a pair of pores.
- Space between the gastric cavity of the gastrozooid and the pneumatophore is occupied by a large cellular mass traversed by canals, the so-called liver, supposed to have an excretory function.
- The reproductive zooids are liberated as free medusae.
- The animal has central disc surrounded by tentacles and all above feature, hence it is Porpita.